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Cross-Wavelet Analysis: a Tool for Detection of Relationships between Paleoclimate Proxy Records 总被引:1,自引:0,他引:1
Cross-wavelet transform (XWT) is proposed as a data analysis technique for geological time-series. XWT permits the detection
of cross-magnitude, phase differences (= lag time), nonstationarity, and coherency between signals from different paleoclimate
records that may exhibit large stratigraphic uncertainties and noise levels. The approach presented herein utilizes a continuous
XWT technique with Morlet wavelet as the mother function, allows for variable scaling factors for time and scale sampling,
and the automatic extraction of the most significant periodic signals. XWT and cross-spectral analysis is applied on computer
generated time-series as well as two independently sampled proxy records (CO2 content approximated from plant cuticles and paleotemperature derived from δ
18O from marine fossil carbonate) of the last 290 Ma. The influence of nonstationarities in the paleoclimate records that are
introduced by stratigraphic uncertainties were a particular focus of this study. The XWT outputs of the computer-models indicate
that a potential causal relationship can be distorted if different geological time-scale and/or large stratigraphic uncertainties
have been used. XWT detect strong cross-amplitudes (∼200 ppm ‰) between the CO2 and δ
18O record in the 20–50 Myr waveband, however, fluctuating phase differences prevent a statistical conclusion on causal relationship
at this waveband. 相似文献
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Plasma of electric arc discharges between composite Cu–W, Cu–Mo and Cu–Cr electrodes in argon flow and their spectra were studied by optical emission spectroscopy. Since values of oscillator strengths for W I, Mo I and Cr I presented in various sources are significantly different, selection of spectroscopic data for these elements (particularly oscillator strength) was expected to be useful for plasma diagnostics. The Boltzmann plot method was used as a tool for the selection of appropriate spectral lines and their spectroscopic data. The main result of the paper is W I, Mo I and Cr I spectral lines and spectroscopic data recommended for diagnostics of plasma with such metal impurities. 相似文献
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Large igneous provinces (LIPs) are considered a relevant cause for mass extinctions of marine life throughout Earth’s history. Their flood basalts and associated intrusions can cause significant release of SO4 and CO2 and consequently, cause major environmental disruptions. Here, we reconstruct the long-term periodic pattern of LIP emplacement and its impact on ocean chemistry and biodiversity from δ34Ssulfate of the last 520 Ma under particular consideration of the preservation limits of LIP records. A combination of cross-wavelet and other time-series analysis methods has been applied to quantify a potential chain of linkage between LIP emplacement periodicity, geochemical changes and the Phanerozoic marine genera record. We suggest a mantle plume cyclicity represented by LIP volumes (V) of V = ?(350–770) × 103 km3 sin(2πt/170 Ma) + (300–650) × 103 km3 sin(2πt/64.5 Ma + 2.3) for t = time in Ma. A shift from the 64.5 Ma to a weaker ~28–35 Ma LIP cyclicity during the Jurassic contributes together with probably independent changes in the marine sulfur cycle to less ocean anoxia, and a general stabilization of ocean chemistry and increasing marine biodiversity throughout the last ~135 Ma. The LIP cycle pattern is coherent with marine biodiversity fluctuations corresponding to a reduction of marine biodiversity of ~120 genera/Ma at ~600 × 103 km3 LIP eruption volume. The 62–65 Ma LIP cycle pattern as well as excursion in δ34Ssulfate and marine genera reduction suggest a not-yet identified found LIP event at ~440–450 Ma. 相似文献
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